When measuring and analyzing a sample such as blood and urine, reagent is generally added to the sample to prepare a measurement sample and the measurement sample is measured to obtain optical characteristics and the like. In blood coagulation measurement, the sample is heated for a predetermined time mainly to stabilize and promote the blood coagulation reaction.
For example, blood coagulation measuring apparatuses heat a blood sample to a predetermined temperature (usually 37° C.) for a predetermined time, and thereafter dispense reagent such as PT reagent and APTT reagent to the sample to prepare a measurement sample. And blood coagulation time is obtained by measuring the optical density of the measurement sample. When the measurement sample is measured, it is desired that the measurement sample is kept under a warm condition in order to stabilize and promote the blood coagulation reaction. However, reagent is kept under a low temperature (normally about 10° C.) before dispensing the reagent to a sample. Therefore, when a cool reagent is dispensed to a heated sample, a temperature of the sample drops and the blood coagulation reaction may not proceed normally.
A heating pipette provided with a heater for heating aspirated reagent is disclosed in, for example, Japanese Patent Laid-Open Publication No. 2004-61173. This kind of heating pipette heats aspirated reagent after setting a target temperature (for example 37° C.), and dispenses the heated reagent to a sample.
However, there are several measurement items in blood coagulation measurement, and a type of reagent and aspiration amount of the reagent vary by the measurement item. Moreover, required degree of heating is influenced by an environmental temperature. Therefore, it is difficult to heat all reagents to a temperature in a predetermined range. If a large amount of reagent is aspirated, even when a target temperature of the reagent is set at 37° C., the reagent may not be heated sufficiently and be discharged in a temperature lower than 37° C. On the other hand, if a small amount of reagent is aspirated, even when a target temperature of the reagent is set at 37° C., the reagent may be heated excessively and be discharged in a temperature exceeding 37° C.
Furthermore, it is necessary to make a space of an opening of a reagent container as small as possible to prevent evaporation of expensive reagent. And it is necessary to decrease an external diameter of the heating pipette which is inserted into the opening of the reagent container when the space of the opening is decreased. It is considered that the reagent container is slightly tilted in order to reduce the reagent dead volume (the amount of unaspiratable liquid remaining at the bottom of the container) and in order to effectively aspirate the reagent within the reagent container by the heating pipette. In this instance, however, the space of the opening decreases when viewed from above (an space which is obtained by projecting an actual opening space on a horizontal plane) as a result of tilting the opening of the reagent container relative to the horizontal plane. Therefore, it is desired to decrease the external diameter of the heating pipette inserted into the opening when the heating pipette is inserted in a vertical direction. The heating pipette is configured by providing a heater inside a long cylindrical pipette. It is difficult to decrease the external diameter of the pipette unless the size of the heater is decreased. When the size of the heater is decreased, the heating capability of the heater becomes less. Therefore, a longer time is necessary to attain the target temperature of 37° C., thus failing to meet the need for high speed processing.